A fuel cell has advantages, such as high efficiency, environment friendliness, high output density, and the like, and also has gained great attention as promising future clean energy technology. An existing low-temperature polymer electrolyte membrane fuel cell (LT-PEMFC) experiences difficulty in its commercialization due to some reasons. A water management system, for example, a humidifier, a water trap, etc., may be used to operate the low-temperature polymer electrolyte membrane fuel cell. In addition, the fuel supply is difficult and hydrogen having a relatively low concentration for specific impurity is to be used. The heat obtainable by operating the low-temperature polymer electrolyte membrane fuel cell has a low exhaust heat temperature and thus, can be limitedly used. As an alternative of the low-temperature polymer electrolyte membrane fuel cell, research on a high-temperature polymer electrolyte membrane fuel cell (HT-PEMFC) is actively ongoing. The high-temperature polymer electrolyte membrane fuel cell may use a polybenzimidazole (PBI)-based electrolyte membrane on which phosphoric acid is doped and may be operable without using separate humidification. In addition, since water generated by the operation of the fuel cell occurs in a form of vapor, a separate water trap is not required. Also, if the high-temperature polymer electrolyte membrane fuel cell is at an operation temperature of 150 to 180° C., poisoning of CO may occur. A performance degradation phenomenon of a membrane electrode assembly (MEA) by such poisoning of CO may be remarkably reduced. Accordingly, the high-temperature polymer electrolyte membrane fuel cell may be resistant up to CO concentration of 3%. Due to the above phenomenon, a CO removal process may be reduced, or alternatively, minimized during a hydrogen reforming process. Also, since a high exhaust heat temperature close to 100° C. may be obtained, thermal energy may be variously available.
However, further developments are still required for the high-temperature polymer electrolyte membrane fuel cell. Theoretically, the high-temperature polymer electrolyte membrane fuel cell has a high electrochemical reaction speed. However, the performance of the actually developed high-temperature polymer electrolyte membrane fuel cell does not reach the performance of the low-temperature polymer electrolyte membrane fuel cell. Due to harsh operating conditions, for example, exposure to phosphoric acid and high temperature, the high-temperature polymer electrolyte membrane fuel cell has a vulnerable durability and a relatively short cell life.
For example, if a portion of the fuel cell is damaged under a high temperature operating condition, a refrigerant may permeate a membrane electrode assembly (MEA) and the performance of the fuel cell may be degraded. Also, oil used as a refrigerant of a high-temperature polymer electrolyte membrane fuel cell stack has a relatively high viscosity. Thus, the oil may cause a high differential pressure in a circulating path, which may also lead to damaging the fuel cell. The oil used as the refrigerant of the high-temperature polymer electrolyte membrane fuel cell stack acts at a high temperature, which may trigger a change in a volume of a separating plate while circulating a refrigerant flow path formed in the separating plate of the fuel cell and may escalate damage.
The information included in this Background section of the specification, including any references cited herein and any description or discussion thereof, is included for technical reference purposes only and is not to be regarded subject matter by which the scope of the invention as defined in the claims is to be bound.